Pocatello, ID

Weather Forecast Office

May 30, 2020 Thunderstorms

Overview

PIH forecasters first noticed weak showers producing severe gusts over northern Utah. SLC passed on storm reports as they received them. First warnings were issued for the Bear Lake area, as a series of storms continued to redevelop across this area. Warnings were prompted due to similar looking activity producing strong gusts in northern Utah. The Bear Lake activity did not produce any events. Next, thunderstorms developed over Box Elder County, UT and produced severe gusts. These gusts streamed northward, and produced a 71 mph wind gust and associated tree and outbuilding damage in Holbrook. Just before this, convection over the eastern Magic Valley prompting a warning for the Burley, Paul, Rupert and Heyburn areas. We received reports from Eric Brill at KMVT of tree damage in Heyburn. This activity raced north through the Central mountains, producing tree damage south of Mackay, outbuilding damage in Darlington, and a 61 mph gust at the Challis ASOS. Meanwhile, the storms racing northward across the Rockland and Arbon Valleys producing 49-54 mph wind gusts in American Falls and Aberdeen, respectively. Soon after, another round of convection and associated outflow raced up the same valleys from northern Utah. 38 power poles were felled and/or snapped just west of Aberdeen, along with numerous reports of tree and building damage in this area. Outbound on the lowest tilt contained a 67 knot pixel in this area. This activity raced raced northward, producing numerous 70-75 mph gusts across the INL. An 83 mph gust was recorded at the Camas ITD site. Tree damage occurred south of Menan with this activity as well.

Wind Damage southwest of Aberdeen. Photo Credit: Idaho Power

Photos & Video
Radar
Storm Reports
Environment

Photos & Video

Social Media


Hail, Wind, Lightning Potential	Severe Tstms Potential - SPC	Boating Impacts	Aviation Impacts

Active Warnings During Event

Other Photos


Down Powerlines west of Aberdeen Photo Credit: Idaho Power	Down Trees west of Aberdeen Photo Credit: Idaho Power	Damaged Powerlines west of Aberdeen Photo Credit: Idaho Power	Tree Damage South of Mackay Photo Crediit: Bryce Woodbury


Lightning NNW of Blackfoot Photo Credit: Alicia Carper	Tree Damage near Heyburn Phot Credit: Eric Brill KMVT	Tree Damage near Holbrook Photo Credit: Steve Hess

Radar

Header

Radar imagery from 4:10 pm to 9:00 pm

Storm Reports

...HIGHEST THUNDERSTORM WIND GUST REPORTS MAY 30TH...
Resent to correct time at Pocatello Airport

Location                     Speed     Time/Date       Lat/Lon             

...Idaho...

...Bannock County...
Fort Hall                    61 MPH    0930 PM 05/30   43.02N/112.41W       

...Bear Lake County...
Grace                        45 MPH    1100 PM 05/30   42.30N/111.40W       

...Bingham County...
Atomic City                  61 MPH    0805 PM 05/30   43.44N/112.81W       
Aberdeen                     54 MPH    0915 PM 05/30   42.95N/112.82W       
Taber                        52 MPH    0800 PM 05/30   43.32N/112.69W       

...Blaine County...
6 S Sun Valley Ohio Gulch    50 MPH    0644 PM 05/30   43.60N/114.32W       
        2.4 SW Ketchum (SNOWNET)     50 MPH    0400 PM 05/30   43.66N/114.40W       
D4 - Smiley Creek Airport    48 MPH    0545 PM 05/30   43.91N/114.80W       

...Bonneville County...
Kettle Butte                 70 MPH    0850 PM 05/30   43.55N/112.33W       
Idaho Falls Airport          46 MPH    0901 PM 05/30   43.52N/112.07W        

...Butte County...
Dead Man Canyon              74 MPH    0840 PM 05/30   43.62N/113.06W       
Specific Manufacturing Capab 51 MPH    0845 PM 05/30   43.86N/112.73W       
5 W Arco                     49 MPH    0747 PM 05/30   43.62N/113.39W       
INTEC/Grid 3                 47 MPH    0740 PM 05/30   43.59N/112.94W       
D6 - Puzzle                  46 MPH    0845 PM 05/30   43.51N/112.89W       

...Cassia County...
Moburg Canyon                57 MPH    0639 PM 05/30   42.04N/113.15W       
Cotton Ridge                 57 MPH    0509 PM 05/30   42.17N/114.20W       
D4 - Yale                    54 MPH    0715 PM 05/30   42.52N/113.42W       
Raft River RAWS              49 MPH    0719 PM 05/30   42.55N/113.26W       
D4 - Idahome Interchange     49 MPH    0700 PM 05/30   42.41N/113.32W       
10 S Oakley                  45 MPH    0545 PM 05/30   42.10N/113.90W       

...Clark County...
D6 - Camas                   83 MPH    0945 PM 05/30   44.16N/112.23W       
D6 - Monida                  52 MPH    1000 PM 05/30   44.53N/112.27W       

...Custer County...
Challis                      61 MPH    0723 PM 05/30   44.52N/114.22W       
Copper Basin                 49 MPH    0850 AM 05/31   43.81N/113.85W       
Stanley Airport              48 MPH    0643 PM 05/30   44.17N/114.93W       
D6 - Willow Creek Summit     46 MPH    0115 AM 05/31   44.23N/113.98W       

...Franklin County...
1.2 NW Preston (UTAH CLIMA)  46 MPH    0415 PM 05/30   42.11N/111.89W       

...Jefferson County...
Rover                        71 MPH    0840 PM 05/30   43.72N/112.53W       
Hamer                        64 MPH    0940 PM 05/30   44.01N/112.24W       
Terreton                     64 MPH    0900 PM 05/30   43.84N/112.42W       
Roberts                      58 MPH    0915 PM 05/30   43.74N/112.13W       
D6 - Osgood                  49 MPH    0914 PM 05/30   43.65N/112.10W       

...Minidoka County...
2.9 W Paul (AGRIMET)         50 MPH    0600 PM 05/30   42.59N/113.84W       
Burley Airport               49 MPH    0809 PM 05/30   42.55N/113.77W       
Minidoka                     49 MPH    0610 PM 05/30   42.80N/113.59W       

...Oneida County...
4 N Holbrook                 71 MPH    0701 PM 05/30   42.22N/112.66W       
D4 - Juniper Interchange     57 MPH    0645 PM 05/30   42.14N/112.98W       

...Power County...
6 NE AMERICAN FALLS          55 MPH    0730 PM 05/30   42.85N/112.77W
American Falls               49 MPH    0735 PM 05/30   42.77N/112.85W
Pocatello Airport            46 MPH    0913 PM 05/30   42.92N/112.57W             

...Teton County...
D6 - Pine Creek Pass         60 MPH    0445 AM 05/31   43.57N/111.22W       

Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers
for their dedication. Not all data listed are considered official.

Environment

As May 30th progressed, a strong area of low pressure moved northward through northern California and into northwest Nevada. Winds aloft increased across the Pacific Northwest, including eastern Idaho as the day progressed. By the early afternoon hours, showers and thunderstorms over northern Utah began to produce outflow winds in the 60-75 mph range. This activity then moved into southern Idaho in 2 waves, with the winds from the first round moving north up the Rockland, Arbon and Raft River Valleys in both waves. Despite a marginal environment for widespread, organized severe thunderstorms, multiple reports of severe thunderstorm winds (defined as 58 mph or greater) were observed. So despite the somewhat unfavorable environment for widespread, organized convective activity, why were such widespread, severe winds observed, even from weaker activity? Plentiful dry air in the low to mid levels of the atmosphere was available, and mixing heights increased through the day to allow for the stronger winds aloft to be made available to mix to the surface. The dry air available in the low and mid-levels of the atmosphere helped facilitate this process. In addition, once showers and thunderstorms developed, the cooling effects from evaporating raindrops helped add velocity to the thunderstorm outflow winds. The relatively flat, tree-less surface of the Snake Plain is a fairly low-friction surface, so thunderstorm outflow winds can continue for miles before slowing down. The discrepancy between the somewhat marginal environmental conditions for widespread, organized thunderstorms and the resultant widespread, severe thunderstorm winds produced by the showers and thunderstorms on May 30 made this an intriguing event to document.

Near-storm Environment Data:


Figure 1: 12z Salt Lake sounding. Inverted V, dry air in lower areas, with 40 knots aloft above the inverted V. Does show a nocturnal inversion	Figure 2: 00z Salt Lake Sounding. Stronger winds aloft. Inverted V with nocturnal inversion gone.	Figure 3: Downcape observed values of 1600. Anything over 1000 is significant.

Synoptic Environment Data:


Figure 1: 12z 300mb winds	Figure 2: 00z 300mb winds	Figure 3: Bulk Shear over 40 is good. They were below 30.

Additional Environmental data:


Figure 1: 12z 500mb winds	Figure 2: 00z 500 mb winds	Figure 3: LCL (Lifted Condensation Level) Anything over 4000 was significant.


Figure 4: Low-level Lapse rates over 9.	Figure 5: Mid-level Lapse rates

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Snow Across the Great Lakes, Central Appalachians, and Northeast; Unsettled Weather in the West

May 30, 2020 Thunderstorms